The present invention relates to endovascular balloons used to recanalize, dilate and/or deploy a stent within a constricted vessel.
Balloon angioplasty for opening a constricted segment of a blood vessel has become a widely accepted therapeutic alternative to coronary and peripheral arterial bypass surgery for many patients.
To deliver a balloon catheter used in balloon angioplasty, a guidewire is advanced through the vasculature across the constricted vessel segment. A dedicated guidewire lumen in the balloon portion of the catheter is fed over the guidewire; the dedicated lumen substantially spanning the longitudinal length of the balloon interior. The balloon is advanced along the guidewire through the vasculature until reaching the constricted vessel segment. The balloon is inflated to apply radial outward pressure against the walls of the constricted vessel segment to restore vessel patency, and normal vessel diameter.
When used to deploy a stent in the constricted vessel segment, the unexpanded stent is mounted around the unexpanded balloon and transported to the constricted vessel segment. Upon reaching the constricted vessel segment, the balloon and stent are expanded, thereby restoring patency and normal vessel diameter to the constricted vessel and providing a structure that will continue to support the vessel wall.
The precise positioning of the balloon against the constricted vessel segment is critical to the success of the procedure; yet, many factors can adversely affect balloon deliverability and precise positioning.
The human vascular tree is far from being uniform in structure and each procedure is a unique experience requiring considerable manual dexterity. With currently available balloon systems, certain lesions are inaccessible and/or exceedingly difficult to reach due to vessel narrowing and rigidity of the treated vessel and lesions. Hence, the unexpanded balloon should be designed with a narrow cross sectional diameter (crossing profile).
Vascular balloon dilation is more challenging when the constricted vessel segment is located within a bifurcation in the vessel: where a sizable side branch vessel bifurcates off a main branch vessel. A common treatment technique consists of inflating two balloons sequentially; a first balloon in the main branch vessel followed by a second balloon in the side branch vessel.
Unfortunately, sequential dilatations are frequently ineffective in treating bifurcated constricted vessels, as the vessel wall at the bifurcation tends to stretch outward; resulting in narrowing of the adjacent branch or shifting atherosclerotic debris from one vessel to the other, referred to as “shifting plaque”.
In order to prevent adjacent branch narrowing, a “kissing balloon” technique has been developed, as described in U.S. Pat. No. 4,896,670 (Crittenden), the entirety of which is incorporated herein by reference. In the kissing balloon technique, a first balloon occupies the proximal main branch vessel (trunk) and a segment of the distal main branch vessel. A second balloon occupies a segment of the proximal main branch (trunk) and a segment of the side branch vessel. Prior to inflation, the proximal portions of the two balloons occupy the proximal main branch vessel sit side-by-side and, upon inflation, the first proximal balloon portion “kisses” the second proximal balloon portion.
The “kissing balloon” technique is not without drawbacks, including:
a) difficulty of coordinating inflation and deflation of two separate balloons using two separate inflators by two operators;
b) creation of asymmetric and non-circular expansion of the proximal main branch (MB) where the “kissing” takes place, potentially causing suboptimal post-inflation results. For example, underexpansion will fail to properly clear the stenotic segments; while overexpansion can cause a dissection (tear) of the vessel wall.
c) balloon slippage during inflation;
d) difficulty in positioning the side-by-side balloon segments due to the large crossing profile created by the separate guidewires and guidewire lumens in each balloon; and
e) difficulty in manipulating the guiding catheters as the catheters must accommodate two separate side-by-side balloons of at least 6 French (2.0 millimeters) or 7 French (2.3 millimeters).
U.S. Pat. No. 4,413,989 (Schjeldahl et al) and U.S. Pat. No. 6,017,324 (Tu, et al), the entirety of which are incorporated herein by reference, disclose a “Y”-shaped balloon, herein bifurcated balloon.
As seen in FIG. 1a, a prior art bifurcated balloon 180 has two guidewire lumens:                a first guidewire lumen 136 passing through a proximal balloon trunk 130 and a first distal balloon branch 132; and        a second guidewire lumen 107 passing through proximal balloon trunk 130 and a second distal balloon branch 134.        
The bifurcated balloon solves some of the problems posed by the kissing balloons. However, when guidewires 106 and 156 are fed through guidewire lumens 136 and 107 respectively, the large crossing profile hinders deliverability and accurate positioning of bifurcated balloon 180.
Additionally, two separate side-by-side guidewire lumens 106 and 156 increase the complexity and cost of manufacturing bifurcate balloon 180.
It would be highly advantageous to have a bifurcated balloon that deploys in bifurcated vessels without having at least some of the disadvantages of the prior art.